Self-assembly and gelation properties of glycine/leucine Fmoc-dipeptides

Self-assembly of aromatic peptide amphiphiles is known to be driven by a combination of pi-pi stacking of the aromatic moieties and hydrogen bonding between the peptide backbones, with possible stabilisation from the amino acid side chains. Phenylalanine-based Fmoc-dipeptides have previously been reported for their characteristic apparent pK(a) transitions, which were shown to coincide with significant structural and morphological changes that were peptide sequence dependent. Here, phenylalanine was replaced by leucine and the effect on the self-assembling behaviour of Fmoc-dipeptides was measured using potentiometry, fluorescence and infrared spectroscopy, transmission electron microscopy, X-ray scattering and shear rheometry. This study provides additional cues towards the elucidation of the sequence-structure relationship in self-assembling aromatic peptide amphiphiles.